This invention relates to the generation of random signals and, more particularly, it relates to the generation of a binary random variable with improved statistical properties.
Random signal sources are widely recognized as providing numerous desirable functions in a variety of applications such as in the fields of communications and testing. One conventional generation technique is to use feedback shift registers to provide a pseudorandom number sequence typically in binary form. Although a pseudorandom sequence may be considered random for some purposes, it is actually not random but deterministic as evidenced by the prefix "pseudo". Other generation techniques utilize a random signal device such as a noise diode but, in the process of deriving a useful binary signal from it, the mathematical characteristics or statistical properties of the binary signal are undesirably modified or biased.
In conventional random signal sources, there are two important statistical measures. In order for the signal to be unbiased, the states of a binary random signal on a statistical average should have equiprobability of occurrence. If the two signal states, for example, are +1 and -1, the statistical mean of the signal should be zero. Also, the bit-to-bit covariance of the signal should be very small. In this way, the use of the history of past signal state sequences to predict the present signal state is made more difficult. Satisfying these two conditions concurrently with low cost circuitry of low complexity has not heretofore been attainable.